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tkamsal's avatar
tkamsal
Explorer
Jul 02, 2014

Gas Gauge Misreading

I have a 1997 Itasca Suncruiser with a Chevy 454 V8 7 Litre engine. I recently had the fuel pump and sending unit replaced at great cost cause the gas gauge had been stuck to past full. It ran OK. After it was fixed it worked on one trip. Now the gauge reads full until about a 1/4 of a tank is used up. It then works normally dropping as I travel. I guesstimate that EMPTY is somewhere near the 1/4 tank mark on the gauge based on 6 days of driving and keeping track of mileage and fuel consumption. Everything else works fine. This is more an irritation than serious problem at this point in time, but would like it to work correctly. I don't want to drop the tank again because of the cost.

Can the gauge needle itself now somehow be adjusted down so it shows correctly?

Ted in Cheverly, MD
Class A

2 Replies

  • Executive45's avatar
    Executive45
    Explorer III
    Jul 02, 2014
    I simply fill up after 1000 miles. That way I never get below 1/4 tank...generator won't run....

    Mine has the sending unit on top of the main tank. Using a mirror and a small screwdriver, I can back the screw out slightly to 'recalibrate' the dash gauge. Yours may be different but see if there's a sending unit on top of the tank....Dennis
  • tatest's avatar
    tatest
    Explorer II
    Jul 02, 2014
    That's fairly common behavior for gauges of that vintage, and the previous 30-40 years, because of the differences in resistance profile of the sending unit and non-linear response of the gauge (whether electromagnetic or bi-metallic). The movement of the float can also be non-linear.

    The calibration point was supposed to be "empty" on the gauge when the float is at the bottom of its travel. Other readings are approximate but reasonably linear, from the point the needle starts moving, which is usually after you've burned off what is in the filler neck (as much as 2 gallons on some vehicles like my Fit) and the first few inches at the top of the tank that may be holding the float at the upper stop.

    I usually refill most vehicles between 1/2 tank and 1/4 tank on the gauge when I find a convenient station (never know how far to the next one) and ever since I've had a trip odometer that is my backup fuel gauge after a fillup, bot not useful on a partial.

    The gauge can be tested for proper response, and the whole instrument cluster for voltage regulation, but with response you are seeing the chances are the fuel gauge will test to be within specs.

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